Ptenothrix Börner, 1906

Cheng, Hsin-Ju, Chang, Bruno Cavalcante Bellini Chih-Han, Janssens, Frans & Nakamori, Taizo, 2024, Positive association between PTN polymorphisms and schizophrenia in Northeast Chinese Han population., Zoological Studies 63 (42), pp. 141-149 : 6-22

Genus Ptenothrix Börner, 1906

Genus diagnosis: Large abdomen without protuberance. Head, large abdomen anteriorly, and Abd VI with large spines (blunt acanthoid chaetae). Large abdomen posteriorly with longitudinal rows of short spines. Bothriotrichia A and D present on adults. Neosminthuroid chaetae missing on the parafurcal area. Dorsal valve of small abdomen dorsally with 5 chaetae arranged in two transverse rows; anterior with 3 chaetae and posterior with 2 robust, large and apically rounded chaetae (blunt acanthoid chaetae). Tibiotarsus III posteriorly with 2 (or rarely 3) modified serrated chaetae. Claws mostly without a tunica. Retinaculum with 4+4 teeth. Outer and inner dorsal chaetae of dens often serrated (based on Yosii and Lee 1963; Yosii 1970; Bretfeld 1999; Fjellberg 2007; Oliveira et al. 2020; Jo and Park 2023).

Type species: Podura atra Linnaeus, 1758 .

Ptenothrix taiwanensis sp. nov. ( Figs. 5A–C, 7–11, 12A, 12C, 13, Table 2) urn:lsid:zoobank.org:act:DC999C0A-A464-458B-99F0-0E65B70FD2CB

Ptenothrix denticulata ( Folsom, 1899) : Cheng et al. 2022, p. 137 –138 (text-fig. 4A).

Type material: TAIWAN: Holotype ñ on slide: Taiwan, New Taipei City, Xindian Dist., Changfu Temple (24.91491, 121.53243), 7, May. 2022. by searching rotten wood, HJ Cheng, DY Cheng, JK Cheng leg. ( NTUE13100001 ). 4 paratypes on slides: 3ñ 1ò, same data as holotype (1ñ 1ò in NTUE: ñ NTUE13100002 , ò NTUE13100003 ; 2ñ in NMNS: 8848-1, 8848-2). 3 paratypes in ethanol: 2ñ 1 sex undetermined (DNA voucher), same data as holotype (1ñ 1 sex undetermined in NTUE: ñ NTUE13100004 , sex undetermined NTUE13100005 ; 1ñ in NMNS: 8848-3).

Other analyzed slide specimens: TAIWAN: 1ñ, Keelung City, Anle Dist., Lover’s Lake Park (25.159123, 121.704894), 23. September. 2022, by searching rotten wood, leg. HJ Cheng, ZJ Chang ( NTUE 13300001); 1ñ, Yilan County, Datong Township (24.619015, 121.679917), 1. October. 2022, by beating vegetation, leg. HJ Cheng, ML Fu ( NMNS: 8848-4); 2ò, Pingtung County, Manzhou Township, 31. June to 4. July. 2009, leg. ML Jeng ( NMNS: 8848-5, 8848-6); 3ñ 1ò, Hualien County, Da Nong Da Fu Forest Park, 18. November to 12. December. 2018, flight interception trap, leg. YH Ho ( NMNS: ñ 8848-7, ñ 8848-8, ñ 8848-9, ò 8848-10); 1ñ 3ò, Tainan City, Dongshan Dist., Shihe Mountain, 27. August to 7. October. 2021, Malaise trap, leg. ML Jeng, YH Ho, WT Yang ( NMNS: ñ 8848-11, ò 8848-12, ò 8848-13, ò 8848- 14); 2ñ 1ò New Taipei City, Fushan Botanical Garden (24.7634, 121.5849), 14. September to 2. October. 2021, flight interception trap, leg. YH Ho, CT Hsu ( NMNS: ñ 8848-15, ñ 8848-16, ò 8848-17); 1ñ, Hsinchu County, Syakaro National Trail, 18. May. 2022, leg. LH Chen ( NTUE 13300002).

Etymology: The name taiwanensis , an adjective meaning “Taiwanese”, is given to this species with reference to its type locality, Taiwan.

Diagnosis: Head vertex with a median longitudinal stripe of dark pigment between the eyes, each eyepatch with a posterior dark spot ( Fig. 5A, C), dorsal large abdomen with a posterior dark spot, small abdomen without any large spot of pigment ( Fig. 5A). Ant II with 3 ( Fig. 7B), Ant III with 10 cup sensilla, distal Ant III partially divided into about 8 pseudo-subsegments ( Fig. 7C), Ant IV with 4 subsegments ( Fig. 7D). Head frontal area with 6+6 spines, D line central spines shorter than the lateral ones, clypeal area with 2 large blunt unpaired central acanthoid chaetae and 2 less thick midfacial unpaired chaetae, b, c, e and f lines with 2 cup sensilla each ( Fig. 8A). Large abdomen anterior Th. II m line with 1+1 or 2+2 large blunt acanthoid chaetae, dorso-posterior region with 4 longitudinal lines of short spines, with 6, 5, 14, 14 spines from the more lateral to the more dorsal line, respectively ( Fig. 9A). Parafurcal area with two cup sensilla, without any serrated chaetae. Dorsal anal valve of small abdomen with as1–2, ms2, ms4 and mps4 as blunt acanthoid chaetae in both sexes; ventral anal valve aai1 of the female and mi1 of both sexes as blunt acanthoid chaetae, 3 chaetae between aai1 and ai 6 in males and females; female subanal appendage smooth, blunt and thick ( Fig. 9B, C). Tibiotarsus III with 2 modified serrated chaetae, 1 microsensillum in a cavity (oval organ), 5 cup sensilla, and 4 oval organs (without inner sensilla) ( Fig. 10F). Ungues with pseudonychia and lacking tunica, with 2 dorsal, 2 internal and 2+2 lateral teeth each, unguiculi with one internal tooth each, apical filaments acuminate or slightly knobbed, surpassing the ungues tip on all legs ( Fig. 11A–C). Manubrium with 8–10 dorsal chaetae on each side. Dens dorsally (posteriorly) with 24 chaetae, 15 of them feathered ( Fig. 11F), dens ventral (anterior) formula from the apex to the basis: 3, 2, 1, 1… 1 ( Fig. 11G).

Description: Average body (head + trunk) length of type series: 2.4 mm in females and 1.77 mm in males, holotype with 2.3 mm. Habitus typical of the genus. Body and appendages with different types of chaetae as presented in figure 4. Specimens in ethanol with background color white to pale yellow, with mottled brown symmetrical longitudinal stripes upon the anterior 4/5 of the dorsum, connected by a stripe and scattered around lateral sides of the body. A dark almost square patch on the bulge of the dorso-posterior large abdomen, small abdomen without any large spot of pigment, head with irregular patterns of pigment, vertex with a longitudinal stripe of dark pigment between eyes, each eyepatch with a posterior dark spot. Ant I red-purple, Ant II basally pale red, apically dark purple, Ant III–IV dark purple. Legs yellowish, banded with three purple stripes on tibiotarsus. Furca pale ( Fig. 5A, B). Most body chaetae smooth (not denticulate).

Head ( Figs. 7–8): Antennae shorter than body, 1.7 mm in holotype. Holotype antennal segment ratio of Ant I:II:III:IV as 1:6.26:8.28:1.57. Ant I with 7 regular chaetae, two of them ventral ( Fig. 7A), Ant II with 20 regular chaetae plus 3 cup sensilla ( Fig. 7B), Ant III distally partially divided into about 8 distal pseudo-subsegments, with 80 regular chaetae, 10 cup sensilla and 1 microsensillum, apical organ typical, with 2 sense rods inside a single shallow invagination ( Fig. 7C), Ant IV with 4 subsegments and about 61 regular chaetae ( Fig. 7D). Head length (along the longitudinal aspect of the body) 306.81 µm in a female paratype (holotype unclear due to position), head height (from mouth to vertex) 560 µm in holotype. Eyes 8+8 with black pigment ( Fig. 13G), eyepatches with 2 interocular spine-like chaetae, the internal larger than the external ( Fig. 8A). Head frontal area with only A, D, E lines, with 2/3/1 spines, respectively (6+6 spines in total), D line central spines shorter than the lateral ones ( Fig. 12A). Interantennal area α, β and γ lines with 2/2/1 short chaetae, respectively; clypeal area a– f lines (dorsal and ventral areas combined) in most specimens with 8(+1)/8(+1)/5/4/4(+1)/5(+1) chaetae respectively; b, c, e and f lines with 2 cup sensilla each; few specimens with chaetae a1, b1 or e1 absent or with extra chaetae between c and b lines ( Fig. 8A). Distal margin of the clypeus with 3 prelabral chaetae, chaetotaxy of labral with 2(+1) p, 2(+1) m + 2 a chaetae, a2 thicker than the others, p0 and p1 chaetae reduced; labrum without clearly formed papillae ( Fig. 8B). Mandibles asymmetrical with 4–6 apical incisive teeth (left with 4–6 teeth, right with 4 teeth) ( Fig. 8C); maxilla capitulum globular, with 6 lamellae, 3 smooth and 3 fringed, without any clear modification ( Fig. 8D); Labial papilla E with 4 guard chaetae, lateral process finger-shaped, almost reaching the apex of the papilla ( Fig. 8E); details of other labial papillae not clearly observable. Maxillary outer lobe with 2 chaetae subequal in length, apical one thicker than the basal one, sublobal plate with 2 chaetae-like appendages ( Fig. 8F). Ventral groove with 1 and 1 surrounding chaetae from lines a and b, respectively, labium basal fields with 4 central (a2 longer than the others) and 5 lateral chaetae ( Fig. 8G).

Trunk (large and small abdomens) ( Fig. 9): Trunk length of the holotype 1.54 mm. Large abdomen ( Fig. 9A): thorax continuous with abdomen, without any visible segmentation or constrictions. Chaetotaxy similar between males and females, Th II with 1 a and 3 to 4 m chaetae, 1+1 or 2+2 of them as large blunt acanthoid chaetae; Th III with 1 a and 3 m chaetae; Abd I with 3 a chaetae; bothriotricha A ( Fig. 13A), B, C present and misaligned, A posteriorly to B–C and on a large papilla with a surrounding cup sensillum, B and C with 4 surrounding chaetae between them, each inside a small papilla; dorso-posterior region with 4 longitudinal lines of spine-like chaetae, with 6/5/14/14 chaetae for the more lateral to the more dorsal line, respectively. Parafurcal area (furca basis) without neosminthuroid chaetae, with 2 cup sensilla, 2 large blunt acanthoid chaetae and 6 to 7 regular chaetae. Bothriothricum D in the large abdomen, in a small papilla. Small abdomen of the female ( Fig. 9B): dorsal anal valve with as1–5, ms1–4, mps1–4, mps’ and ps1–2 chaetae, as1, ms1 and ps1 unpaired; as4–5 as cup sensilla, as1–2, ms2, ms4 and mps4 as blunt acanthoid chaetae, ms3 as a S chaeta; ventral anal valves each with aai1, ai1–6, ami1–2, mi1– 5, mpi1–2 and pi1–3 chaetae, ami2 as an oval organ; ai1 as a cup sensillum, ai2–3 as S chaetae, aai1 and mi1 as a blunt acanthoid chaetae, mi5 as the subanal appendage, smooth, blunt and thick. Another interpretation of the small abdomen chaetotaxy following Yosii and Lee (1963) in fig. 9C. Genital plate of the female lacking dorsal chaetae, ventral area with 7 to 9 chaetae on each side ( Fig. 9D). Small abdomen of male ( Fig. 9E): dorsal anal valve with as1–5, ms1–4, mps1, mps4, mps’ (present or absent), and ps1–2 chaetae, as1, ms1, ps1 unpaired, as4–5 as cup sensilla, as1–2, ms2, ms4, mps4 as blunt acanthoid chaetae, ms3 as a S chaeta; ventral anal valves each with aai1, ai1–6, ami1–2, mi1–5 and pi1–3 chaetae, ai1 as a cup sensillum, ai2–3 as S chaetae, ami2 as an oval organ, mi1 as a blunt acanthoid chaeta; 3 chaetae between aai1 and ai 6 in males ( Figs 9B, E and 12C) and females. Another interpretation of the small abdomen chaetotaxy following Yosii & Lee (1963) in fig. 9F. Genital plate of male densely covered by chaetae, number unclear.

Large abdomen appendages ( Figs. 9A, 10, 11): Epicoxa, subcoxa and coxa I with 0, 1, 0 chaetae, respectively ( Fig. 9A); trochanter I with 4 regular chaetae; femur I with 12 regular chaetae plus 1 microsensillum in a cavity (oval organ) ( Fig. 13E) and 1 cup sensillum ( Figs. 10A, 13B); tibiotarsus I with 40 regular chaetae plus 1 microsensillum in a cavity (oval organ), 3 cup sensilla and 4 oval organs ( Fig. 13D, without inner sensilla), distal whorl with 8 chaetae ( Fig. 10B). Epicoxa, subcoxa and coxa II with 1, 1, 3 chaetae, respectively ( Fig. 9A); trochanter II with 5 regular chaetae; femur II with 14 regular chaetae plus 1 microsensillum in a cavity (oval organ) and 1 cup sensillum ( Fig. 10C); tibiotarsus II with 41 regular chaetae plus 1 microsensillum in a cavity (oval organ), 3 cup sensilla and 4 oval organs (without inner sensilla), distal whorl with 9 chaetae ( Fig. 10D). Epicoxa, subcoxa and coxa III with 1, 1, 5 chaetae (including one apical small acanthoid chaetae), respectively ( Fig. 9A); trochanter III with 6 regular chaetae; femur III with 14 regular chaetae plus 1 microsensillum in a cavity (oval organ) and 1 cup sensillum ( Fig. 10E); tibiotarsus III with 37 regular chaetae plus 2 modified serrated chaetae ( Fig. 13F), 1 microsensillum in a cavity (oval organ), 5 cup sensillum, and 4 oval organs (without inner sensilla), distal whorl with 9 chaetae ( Fig. 10F), number of teeth on modified serrated chaetae variable, from 4 to 7. Tibiotarsus I with an apical sinusoid chaeta bending across the unguiculus. Inner apical macrochaeta spiky in tibiotarsus I ( Fig. 10B), and blunt in tibiotarsi II – III ( Fig. 10D, F). Foot complexes I–III with 2 small pretarsal chaetae each, 1 anterior and 1 posterior; ungues with 2 unpaired inner teeth subequal in size, lateral lamellae with 2+2 teeth ( Fig. 13K, some specimens with an extra basal smaller tooth in the fore and mid legs), pseudonychia present ( Fig. 13L), merged to the dorsal face with 2 unpaired dorsal teeth, the proximal one smaller, with lateral margins irregularly serrate. Unguiculi with 1 basal tooth and 1 axial filament surpassing the tip of the ungues, apical filaments acuminate or slightly knobbed ( Fig. 11A – C). Collophore with 1+1 chaetae on corpus plus 1+1 distal chaetae on lateral flaps, with a pair of long and warty sacs as typically seen in Dicyrtomidae ( Fig. 13H, I). Tenaculum typically with a quadridentate ramus, corpus with 4 apical chaetae ( Fig. 13J). Furcal size length in holotype as manubrium = 168.48 µm; dens = 556.21 µm; and mucro = 176.94 µm. Manubrium with 8 to 10 dorsal (posterior) chaetae on each side ( Fig. 11E); dens dorsally (posteriorly) with 24 chaetae: 10 on the dorso-external (E1–10), 10 on the dorso-internal (J1–10) and 4 dorso-central ( PE 1–4) chaetae, respectively, external and internal chaetae feathered ( Fig. 13C), except for the chaetae near the manubrium and an apical-external one ( Fig. 11F); dens ventrally (anteriorly) with 8 chaetae, with the following formula from the apex to the basis: 3, 2, 1, 1… 1 ( Fig. 11G); mucro with a narrow apex, with both edges serrated, with about 33 (inner) and 28 (outer) serrations on each edge, with an apical notch ( Fig. 11H). Ratio mucro: dens: manubrium in holotype 1: 3.3: 1.05.

Distribution: Low elevation of Taiwan (mainly the northern and central region), and one locality in Nangan Island, Matsu (public toilet of Mt. Yuntai).

Habitat: Most Dicyrtomidae , including Ptenothrix taiwanensis sp. nov. are atmobiotic ( Bretfeld 1999). Specimens of the new species generally inhabit wet rotten wood and dead leaves of tree ferns and Miscanthus bushes. Some specimens were also found associated with the leaf litter layer, especially juveniles. Sampling localities of Ptenothrix taiwanensis sp. nov. are presented as orange dots in figure 1.

Remarks: Ptenothrix taiwanensis sp. nov. specimens were identified as Ptenothrix denticulata ( Folsom, 1899) in Cheng et al. (2022), which is now proven to be a misidentification (see Fig. 6 and Table 2). Ptenothrix taiwanensis sp. nov. is remarkably similar to Ptenothrix matsuensis sp. nov., described in the next section. We consider both to be cryptic species due to their strong resemblance in color pattern and overall chaetotaxy. In addition to Taiwan Island, P. taiwanensis was also collected on the tile wall in a public toilet in Nangan Island in Matsu, but was not found in any other localities in Matsu. This made us presume that the record in Matsu could be due to recent human intervention.

Compared with other Ptenothrix species found in the vicinities specimen collection, such as Taiwan and South China, Japan, and the type locality of P. denticulata ( Table 2), the two new species differ from the others by: frontal head A internal spines as long as lateral ones (shorter than the lateral ones in P. denticulata ( Folsom, 1899) and longer in P. denticulata catenata Börner, 1909 , P. corynophora Börner, 1909 P. gigantisetae Lin & Xia, 1985 , and P. huangshanensis Chen & Christiansen, 1996 ), Ant IV with 4 subdivisions (2–4 in P. denticulata , 2–3 in P. corynophora , 5 in P. huangshanensis , and 7 in P. gaoligonshanensis Itoh & Zhao, 2000 ), and dorsal dens with 10 inner chaetae (9 in P. annulatus , P. dinghuensis , P. gigantisetae , P. palmisetacea , and P. sinensis ). Further comparisons are listed in table 2.

Ptenothrix matsuensis sp. nov. ( Figs. 5D–F, 12B,12D, 14, Table 2) urn:lsid:zoobank.org:act:B784F1E5-234C-4B42-8F29-F6B96A9AE17A

Type materials: TAIWAN: Holotype ñ on slide, Lienchiang County, Nangan Township, Shengtian Park (26.154204, 119.916068), 25. May. 2023, by beating vegetation, leg. HJ Cheng, YH Ho ( NTUE13100006 ). 4 paratypes on slides: 2ñ 2ò, same data as holotype (1ò 1ñ in NTUE: ò NTUE13100008 , ñ NTUE13100007 , 1ò 1ñ in NMNS: ò 8848- 18, ñ 8848-19). 2 paratypes in ethanol: 1ò 1 sex undetermined (DNA voucher), Lienchiang County, Nangan Township , Motianling (Skyscraper Ridge) Trail (26.161192, 119.953177), 25. May. 2023, by beating vegetation, leg. HJ Cheng, YH Ho (1ò 1 sex undetermined in NTUE: ò NTUE13100009 , sex undetermined NTUE13100010 ).

Other analyzed slide specimens: TAIWAN: 3ñ on slide, Lienchiang County, Nangan Township, Siwei Rd. (26.173417, 119.917225), 25. May. 2023, leg. HJ Cheng, YH Ho (2 in NTUE: NTUE 13300003 and NTUE 13300004; 1 in NMNS: 8848-20). 3ò on slide, Lienchiang County, Nangan Township, Motianling (Skyscraper Ridge Trail) (26.161192, 119.953177), 25. May. 2023, leg. HJ Cheng, YH Ho (1 in NTUE: NTUE 13300005; 2 in NMNS: 8848-21, 8848-22).

Etymology: The new species was named after its type locality, Matsu Islands.

Diagnosis: Head vertex without a longitudinal stripe of dark pigment between eyes, each eyepatch with a posterior dark spot ( Fig. 5D), dorsal large abdomen lacking any dark spot, dorsal small abdomen almost entirely covered by a large patch of dark pigment ( Fig 5D). Ant II with 3, Ant III with 10 cup sensilla, distal Ant III partially divided into about 8 pseudo-subsegments, Ant IV with 4 subsegments. Head frontal area with 6+6 spines, D line central spines as long as the lateral ones ( Figs. 12B, 14A), clypeal area with 2 large blunt unpaired central acanthoid chaetae and 2 less thick midfacial unpaired chaetae, b, c, e and f lines with 2 cup sensilla each. Large abdomen Th. II anterior m line with 1+1 large blunt acanthoid chaetae, dorso-posterior region with 4 longitudinal lines of short spines, with 5–6/ 5/ 12–14/ 12–14 spines from the more lateral to the more dorsal line, respectively ( Fig. 14B). Parafurcal area with two cup sensilla, without any serrated chaetae. Dorsal anal valve of small abdomen with as1–2, ms2, ms4 and mps4 as blunt acanthoid chaetae in both sexes; ventral anal valve aai1 of the female and mi1 of both sexes as a blunt acanthoid chaetae, 3 chaetae between aai1 and ai 6 in females, only 2 in males ( Figs. 12D, 14C); female subanal appendage smooth, blunt and thick. Tibiotarsus III with 2 modified serrated chaetae, 1 microsensillum in a cavity (oval organ), 5 cup sensilla, and 4 oval organs (without inner sensilla) (as in Fig. 10F). Ungues with pseudonychia and lacking tunica, with 2 dorsal, 2 internal and 2+2 lateral teeth each, unguiculi with one internal tooth each, apical filaments acuminate or slightly knobbed, surpassing the ungues tip in all legs (as in Fig. 10A – C). Manubrium with 7 dorsal chaetae on each side ( Fig. 14D). Dens dorsally (posteriorly) with 24 chaetae, 15 of them feathered (as in Fig. 11F), dens ventral (anterior) formula from the apex to the basis: 3, 2, 1, 1… 1 (as in Fig. 11G).

Description: Average body (head + trunk) length of type series: 1.82 mm in females and 1.38 mm in males, holotype with 1.9 mm. Habitus typical of the genus. Overall chaetotaxy similar to Ptenothrix taiwanensis sp. nov. Head vertex without a longitudinal stripe of dark pigment between eyes, each eyepatch with a posterior dark spot ( Fig. 5D), dorsal large abdomen lacking any dark spot, dorsal small abdomen almost entirely covered by a large patch of dark pigment. Ant I red-purple, Ant II basally pale red, apically dark purple, Ant III–IV dark purple. Legs yellowish, banded with three purple stripes on tibiotarsus. Furca pale. Most body chaetae smooth (not denticulate).

Head: Antennae shorter than body, 1.27 mm in holotype. Holotype antennal segments ratio of Ant I:II:III:IV as 1:6.73:7.7:1.8. Antennal chaetotaxy as in Ptenothrix taiwanensis sp. nov., with no observable differences between the two species, Ant I with 7 regular chaetae, two of them ventral (as in Fig. 7A), Ant II with 20 regular chaetae plus 3 cup sensilla (as in Fig. 7B), Ant III distally partially divided into about 8 distal pseudo-subsegments, with 80 regular chaetae, 10 cup sensilla and 1 microsensillum, apical organ typical, with 2 sense rods inside a single shallow invagination (as in Fig. 7C), Ant IV with 4 subsegments and about 61 regular chaetae (as in Fig. 7D). Head length (along the longitudinal of the body) 243.5 µm in a female paratype (holotype unclear due to position), head height (from mouth to vertex) 613.97 µm in holotype. Head chaetotaxy mostly similar to Ptenothrix taiwanensis sp. nov. Eyes 8+8 with black pigment, eyepatches with 2 interocular spine-like chaetae, the internal larger than the external one ( Fig. 14A). Head frontal area with only A, D, E lines, with 2/3/1 spines, respectively (6+6 spines in total), D line central spines sharp and as long as the lateral ones ( Figs. 12B, 14A). Interantennal area α, β and γ lines with 2/2/1 short chaetae, respectively (as in Fig. 8A); clypeal area a–f lines (dorsal and ventral areas combined) with 8(+1)/8(+1)/5/4/4(+1)/5(+1) chaetae respectively; b, c, e and f lines with 2 cup sensilla each. Distal margin of the clypeus with 3 prelabral chaetae, chaetotaxy of labral with 2(+1) p, 2(+1) m + 2 a chaetae, a2 thicker than the others, p0 and p1 chaetae reduced; labrum without clear formed papillae (as in Fig. 8B). Mandibles asymmetrical with 4–6 apical incisive teeth (left with 6 teeth, right with 4 teeth); maxilla capitulum globular, with 6 lamellae, 3 smooth and 3 fringed, without any clear modification (as in Fig. 8C and D). Labial papilla E with 4 guard chaetae, lateral process finger-shaped, almost reaching the apex of the papilla (as in Fig. 8E). Maxillary outer lobe with 2 chaetae subequal in length, apical one thicker than the basal one, sublobal plate with 2 chaetae-like appendages (as in Fig. 8F). Ventral groove with 1 and 1 surrounding chaetae from lines a and b, respectively, labium basal fields with 4 central (a2 longer than the others) and 5 lateral chaetae (as in Fig. 8G).

Trunk (large and small abdomens): Trunk length of holotype 1.31 mm. Large abdomen: thorax continuous with abdomen, without any visible segmentation or constrictions. Chaetotaxy similar between males and females, and almost identical to Ptenothrix taiwanensis sp. nov. Th II with 1 a and 3 to 4 m chaetae, none as large blunt acanthoid chaetae; Th III with 1 a and 3 m chaetae; Abd I with 3 a chaetae; bothriotricha A, B, C present and misaligned, A posteriorly to B–C and on a large papilla with a surrounding cup sensillum, B and C with 4 surrounding chaetae between them, each inside a small papilla; dorso-posterior region with 4 longitudinal lines of spine-like chaetae, with about 5–6/5/12–14/12– 14 chaetae for the more lateral to the more dorsal line, respectively ( Fig. 14B). Parafurcal area (furca basis) without neosminthuroid chaetae, with 2 cup sensilla, 2 large blunt chaetae and 7 regular chaetae. Bothriothricum D in the large abdomen, in a small papilla (as in Fig. 9A). Small abdomen of the female: dorsal anal valve with as1–5, ms1–4, mps1–4, mps’ and ps1–2 chaetae, as1, ms1 and ps1 unpaired; as4–5 as cup sensilla, as1–2, ms2, ms4 and mps4 as blunt acanthoid chaetae, ms3 as a S chaeta; ventral anal valves each with aai1, ai1–6, ami1–2, mi1–5, mpi1–2 and pi1–3 chaetae, ami2 as an oval organ; ai1 as a cup sensillum, ai2–3 as S chaetae, aai1 and mi1 as a blunt acanthoid chaetae, mi5 as the subanal appendage, smooth, blunt and thick; 3 chaetae present between aai1 and ai6 (as in Fig. 9B). Small abdomen of male: dorsal anal valve with as1–5, ms1–4, mps1, mps4, mps’, and ps1–2 chaetae, as1, ms1, ps1 unpaired, as4–5 as cup sensilla, as1–2, ms2, ms4, mps4 as blunt acanthoid chaetae, ms3 as S chaeta; ventral anal valves each with aai1, ai1–6, ami1–2, mi1– 5 and pi1–3 chaetae, ai1 as a cup sensillum, ai2–3 as S chaetae, ami2 as an oval organ, mi1 as a blunt acanthoid chaeta; 2 chaetae present between aai1 and ai6 ( Figs. 12D, 14C). Genital plates of female and male unclear.

Large abdomen appendages: overall chaetotaxy of legs, ventral tube, tenaculum and furca as described to Ptenothrix taiwanensis sp. nov. Epicoxa, subcoxa and coxa I with 0, 0, 1 chaeta, respectively; trochanter I with 4 regular chaetae (as in Fig. 9A); femur I with 12 regular chaetae plus 1 microsensillum in a cavity (oval organ) and 1 cup sensillum (as in Fig. 10A); tibiotarsus I with 40 regular chaetae plus 1 microsensillum in a cavity (oval organ), 3 cup sensilla and 4 oval organs (without inner sensilla), distal whorl with 8 chaetae (as in Fig. 10B). Epicoxa, subcoxa and coxa II with 1, 1, 3 chaetae, respectively (as in Fig. 9A); trochanter II with 5 regular chaetae; femur II with 14 regular chaetae plus 1 microsensillum in a cavity (oval organ) and 1 cup sensillum (as in Fig. 10C); tibiotarsus II with 41 regular chaetae plus 1 microsensillum in a cavity (oval organ), 3 cup sensilla and 4 oval organs (without inner sensilla), distal whorl with 9 chaetae (as in Fig. 10D). Epicoxa, subcoxa and coxa III with 1, 1, 5 chaetae (including one apical small acanthoid chaetae), respectively (as in Fig. 9A); trochanter III with 6 regular chaetae; femur III with 14 regular chaetae plus 1 microsensillum in a cavity (oval organ) and 1 cup sensillum (as in Fig. 10E); tibiotarsus III with 37 regular chaetae plus 2 modified serrated chaetae, 1 microsensillum in a cavity (oval organ), 5cup sensillum, and 4 oval organs (without inner sensilla), distal whorl with 9 chaetae, number of teeth on modified serrated chaetae variable, from 4 to 7 (as in Fig. 10F). Tibiotarsus I lacking any apical bent sinusoid chaeta. Inner apical macrochaeta spiky in tibiotarsus I and blunt in tibiotarsi II – III (as in Fig. 10B, D and F). Foot complexes I – III similar to Ptenothrix taiwanensis sp. nov., with 2 small pretarsal chaetae each, 1 anterior and 1 posterior; ungues with 2 unpaired inner teeth subequal in size, lateral lamellae with 2+2 teeth, duplicate teeth not seen, pseudonychia present, merged to the dorsal face with 2 unpaired dorsal teeth, the proximal one smaller, with lateral margins irregularly serrate. Unguiculi with 1 basal tooth and 1 axial filament surpassing the tip of the ungues, apical filaments acuminate or slightly knobbed (as in Fig. 11A–C). Collophore with 1+1 chaetae on corpus plus 1+1 distal chaetae on lateral flaps (as in Fig. 11D), with a pair of long and warty sacs. Tenaculum with a quadridentate ramus, corpus with 4 apical chaetae. Furcal size length in holotype as manubrium = 153.62 µm; dens = 421.74 µm; and mucro = 149.07 µm. Manubrium with 7 dorsal (posterior) chaetae on each side ( Fig. 14D); dens dorsally (posteriorly) with 24 chaetae: 10 on the dorso-external (E1–10), 10 on the dorso-internal (J1–10) and 4 dorso-central ( PE 1–4) chaetae, respectively, external and internal chaetae feathered, except for the chaetae near the manubrium and an apical-external one (as in Fig. 11F); dens ventrally (anteriorly) with 8 chaetae, with the following formula from the apex to the basis: 3, 2, 1, 1… 1; mucro with a narrow apex, with both edges serrated, with about 46 (inner) and 34 (outer) serrations on each edge, with an apical notch. Ratio mucro: dens: manubrium in holotype 1: 2.83: 1.03.

Distribution: Nangan Island, Matsu, Taiwan. Habitat: Specimens of Ptenothrix matsuensis sp. nov. were found on dead leaves of tree ferns and Miscanthus bushes, similarly to Ptenothrix taiwanensis sp. nov. Sampling localities are presented as green triangles in figure 1. It is noteworthy that Ptenothrix matsuensis sp. nov. was only found during the wet season in Nangan Island, while no specimens were collected during the dry season, a condition that could be related to the life history of the species.

Remarks: Ptenothrix matsuensis sp. nov. is remarkably similar to P. taiwanensis sp. nov. in overall morphology ( Fig. 5), but they appeared as distinct taxa in our analyses of COI phylogeny ( Fig. 6) and K2P distances ( Table 1). Even so, P. matsuensis sp. nov. can be objectively distinguished from P. taiwanensis sp. nov. by: head vertex with an unclear or absent central longitudinal pigment (with a central longitudinal stripe of dark pigment in the latter), frontal head D internal spines as long as the lateral ones (shorter than the lateral ones in P. taiwanensis sp. nov.), manubrium with 7 dorsal chaetae (vs. 8–10 in P. taiwanensis sp. nov.), and only 2 chaetae present between aai1 and ai 6 in the small abdomen of the male of P. matsuensis sp. nov. (3 chaetae present in the male of P. taiwanensis sp. nov.) ( Fig. 12). For further comparisons between similar species of Ptenothrix from Taiwan, South China and Japan, see table 2.

Lectotype designation of Ptenothrix denticulata ( Folsom, 1899)

The type material of Papirius denticulatus Folsom, 1899 in NMNH is a slide-mounted specimen, and is labeled as “ Ptenothrix (Papirius) denticulatus (sic) (Folsom) Type No 5076” and “Komaba, Tokyo, Japan. Coll. C. Ishikawa. Nov. 6. 1894. Lectotype det. by J. T. Salmon, 1938”. Although the specimen is labeled as “ lectotype ” on the slide, the lectotype designation was never formally published, rendering it an invalid type designation under ICZN Art. 74. In 1938, while planning to write a monograph on Collembola of the world, Salmon visited the museums as part of a tour in various institutions in Europe, Great Britain, and the United States to examine and re-describe poorly described Collembola type specimens. Nevertheless, the monograph was never finished. In 1974, the author published the drawings he had completed in the Zoology Publications from Victoria University of Wellington ( Salmon 1974), but Ptenothrix denticulata was not included in this article (Dana M. De Roche, personal communication, January. 12. 2023). As a result, we herein designate the specimen of Papirius denticulatus Folsom, 1899 in the Smithsonian Institution National M u s eu m o f N atu r al H is to r y, Was h in g ton, U S A (catalog no. USNMENT01747048) as the lectotype for Ptenothrix denticulata ( Folsom 1899) .